The Siemens 3RV2902-1AV1 is a SIRIUS undervoltage release designed specifically for 3RV2 motor circuit breakers. It drops the breaker when the control supply voltage falls below its dropout threshold, providing undervoltage protection for motor loads. It snaps onto the same DIN rail as the breaker, occupying minimal panel width at 19 mm.
Voltage ratings and application fit
The control supply is AC only, 50 to 60 Hz, so this release is not compatible with DC control circuits. Maximum break time is 20 ms, fast enough to clear the breaker before motor speed drops into a damaging regime.
Mechanical integration and wiring
The release fits the same rail footprint as the 3RV2 breaker it serves. Dimensions are 68 mm deep, 19 mm wide, 90 mm tall — the narrow width means it doesn't consume an extra module position beyond the breaker's own width. Wiring is via screw-type terminals for the auxiliary and control circuit. The release has no auxiliary contacts (zero CO, zero NC instantaneous contacts), so it does not provide a status feedback signal to a PLC or indicator light. If feedback is needed, a separate auxiliary contact block must be added to the breaker assembly.
Compatibility with 3RV2 breaker sizes
This undervoltage release is listed for use with 3RV2 circuit breakers in frame sizes S00, S0, S2, and S3. That covers the full SIRIUS motor-protective breaker range from the smallest S00 (up to about 16 A motor full-load current) through the S3 (up to about 100 A). The release mounts directly onto the breaker's side without additional adapters. The short-circuit protection design for the release circuit itself is fuse-based — the installer should size the control-circuit fuse per Siemens guidelines.